1. Field of the Invention
The invention relates to a batch, semi-continuous or continuous process for the manufacture of bisphenol-A.
2. Brief Description of Related Art
The dihydric phenol 2,2 bis(p-hydroxyphenyl) propane (commonly referred to as"bisphenol-A", "BPA" or"pp-BPA") is commercially prepared by condensing 2 moles of phenol with a mole of acetone in the presence of an acid catalyst. The phenol is present in the reaction in a molar excess of the stoichiometric requirement. During the condensation, a number of by-products such as isomeric forms of BPA are formed which are considered contaminants of the desired product, BPA. These contaminants are carried in the product stream from the condensation reaction zone, referred to as the condensation product effluent, along with water, unreacted phenol, possibly unreacted acetone and possibly trace quantities of acidic materials derived from the catalyst. Currently, the purification of the desired product BPA is a costly and multi-step procedure.
There are two commercially important processes for the synthesis of BPA currently in use. One process is sometimes called the"HCl" process, in reference to the acidic catalyst employed (hydrogen chloride).
The second synthesis involves the use of an active ion exchange catalyst and is sometimes called the"IER" process, in reference to the ion exchange resin employed. Both syntheses involve passing phenol, acetone and recycled by-products through a reactor containing an acid catalyst followed by a BPA purification scheme.
The "IER process" can be done in one of two ways; first, until essentially complete acetone depletion; second, and most desirable, is "partial acetone conversion". This technology is described in U.S. Pat. No. 5,315,042 which is hereby incorporated herein by reference thereto. The BPA reaction can be optionally promoted by the presence of a free mercaptan such as 3-mercaptopropionic acid, or use a promoter which is chemically or covalently bonded to the IER resin, or use no promoter. These resins are generally well known compositions as are methods of their preparation; see for example the preparative procedures described in U.S. Pat. No. 3,037,052 which is hereby incorporated herein by reference thereto.
The HCl process reaction effluent contains phenol, BPA, a 1:1 adduct of BPA and phenol, isomeric by-products of BPA and impurities along with the promoter (when present) and possibly unreacted acetone. This effluent, also sometimes referred to as the HCl process reaction effluent, may be fed to a stripping operation which removes the water of reaction, HCl, phenol and possibly residual acetone and/or promotor.
Representative of more detailed descriptions of the above processes for condensing phenol with acetone to obtain BPA are those found in the U.S. Pat. No. 4,346,247; 4,396,728; 4,400,555; 4,424,283; 4,584,416; 4,766,254 and 4,847,433; all of which are incorporated herein by reference thereto. The factor shared by all of these known methods and processes is the need to purify and recover the product BPA. This can be done by the 1:1 BPA/Phenol adduct crystallization (U.S. Pat. No. 5,210,329) as the desired BPA forms a 1:1 adduct with excess phenol.
The present invention is a modified process for producing purified BPA in a fully integrated, batch, semi-continuous or continuous commercial process beginning with the condensation reaction product.